Cited references are listed later in this patent application.
Dip-Pen Nanolithography printing allows one to directly print a wide variety of materials including biomaterials including, for example, DNA, phospholipids and proteins on a surface with high-registry and sub-50 nm resolution.[1-3] The development of massively parallel DPN has substantially increased the throughput of DPN through the use of two-dimensional (2D) pen arrays comprising as many as 55,000 AFM cantilevers per cm2.[4, 5] Nevertheless, facile multiplexing, or the ability to simultaneously generate structures made of different materials, still is a challenge in developing a suite of DPN-based nanofabrication tools. Additionally, inconsistent and non-uniform inking from the solutions onto the writing instrument can in some cases hinder advancement of DPN for a particular application.
Hong et al. first demonstrated the direct DPN patterning of two different inks, 16-mercaptohexadecanoic acid (MHA) and 1-octadecanethiol (ODT) with high registry using different tips in a serial process.[16] This approach can provide in some cases insufficient control over the diffusion rates of the two inks and the corresponding linewidths of the nanostructures generated in the experiment. Later, researchers developed microscopic inkwells that can be filled with various inks through integrated microfluidic channels. See for example U.S. Pat. No. 7,034,854. These inkwells are used to address the different pens in a one-dimensional (1D) cantilever array for simultaneous DPN patterning of multiple inks from a single pen array.[17] This technique allows one to ink a linear pen array with up to 8 different inks in a single step, depending on the number of available inkwells.[18] Although this approach works well for many applications including some research applications where a few inks are being integrated in the context of a linear cantilever comprised of relatively few pens, the method is not directly scalable to 2D arrays consisting of thousands or even millions of pens. For instance, such an inkwell chip containing 55,000 individually addressable ink wells in one cm2 might need more than 0.5 m2 just to accommodate the area occupied by the ink reservoirs.
Such capabilities are desirable because they may allow researchers to, for example: (i) fabricate nanoarrays[6-10] with unprecedented chemical and biochemical complexity; (ii) control materials assembly through the use of affinity templates[11, 12] such that each patterned feature controls the placement of different building blocks for making higher-ordered architectures; and (iii) develop an understanding of multivalent interactions between patterned surfaces and proteins, viruses, spores, and cells on a length scale that is biologically meaningful.[13-15] Methods for multiplexing in the context of a DPN experiment thus far have been in general limited due to the challenges associated with addressing and inking each pen of an array with different molecules.
Therefore, a need exists to develop an inking technique that allows one, for example, to coat more uniformly substantially the same amount of ink to different pens within an array, to control the diffusion rates of the different molecules in the ink, and to ink each pen within an array with independent addressability.